JPH0432127B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for producing a high magnetic flux density unidirectional electrical steel sheet with excellent core loss properties for use in iron cores of transformers and the like. [Prior Art] Unidirectional electrical steel sheets are soft magnetic materials that are mainly used as iron core materials for transformers and other electrical equipment, and must have good excitation characteristics and iron loss characteristics. Usually B ₈ is used as a numerical value representing excitation characteristics.
(magnetic flux density at a magnetic field strength of 800 A/m), W _17/50 (at 50 Hz) is used as a value representing iron loss characteristics.
The iron loss per 1 kg when magnetized to 1.7 T is used. This unidirectional electrical steel sheet usually uses the secondary recrystallization phenomenon to form a {110} surface on the steel sheet surface and a <001> surface in the rolling direction.
It is obtained by developing a tissue with an axis. In order to obtain good magnetic properties, it is important that the <001> axis, which is the axis of easy magnetization, is highly aligned in the rolling direction. Also, the plate thickness, specific resistance, purity of the steel plate, etc. have a large effect on the magnetic properties. On the other hand, due to the rise in energy prices in recent years, transformer manufacturers are increasingly focusing on materials for low core loss transformers. In recent years, magnetic domain control technology using lasers has been developed as a measure to reduce iron loss.
As a result, the iron loss characteristics were significantly improved. In addition, the need to develop products with thinner plates and high magnetic flux densities has increased because the thinner the product plate is and the higher the magnetic flux density, the greater the effect of magnetic domain control technology. An effective method for increasing magnetic flux density is to use AlN as an inhibitor and perform final heavy reduction cold rolling with a rolling reduction of more than 80%. There is a problem of stabilization. As a method to solve this problem, a method has been proposed in which hot-rolled sheet annealing is performed, followed by cold rolling and intermediate annealing in sequence, followed by cold rolling with a final heavy reduction of more than 80% (U.S. Pat. No. 3,632,456).
No. Specification). It is true that this method alleviates the instability of secondary recrystallization when the plate thickness becomes thinner, but it is difficult to obtain sufficiently satisfactory iron loss characteristics due to factors such as a decrease in magnetic flux density. These problems remain to be solved in order to manufacture products with high magnetic flux density and excellent iron loss characteristics, even in thin plates. In addition, in the production of high magnetic flux density unidirectional electrical steel sheets by one-time strong reduction cold rolling at a reduction rate of 81 to 95% using AlN as an inhibitor, aging treatment is performed between passes of the above-mentioned strong reduction cold rolling. It has been reported that the magnetic properties are improved by this technology (Japanese Patent Publication No. 13846/1983), but with this technology, products with excellent iron loss properties and high magnetic flux density,
For example, it is not sufficient to manufacture thin plates with a thickness of 0.20 mm or less. [Problems to be solved by the invention] According to the present invention, when producing unidirectional electrical steel sheets using AlN as the main inhibitor, it is impossible to obtain high magnetic flux density, especially in thin products, and therefore it is difficult to obtain good iron loss characteristics. This provides a method to solve this problem. [Means for solving the problem] The present invention uses AlN as the main inhibitor, and hot-rolled silicon steel sheet is subjected to hot-rolled sheet annealing to achieve a rolling reduction of more than 80% to 95%.
In a method for producing a grain-oriented electrical steel sheet by performing two or more cold rollings including final cold rolling with a heavy reduction of %, intermediate annealing performed in between, decarburization annealing after the final cold rolling, and final finishing annealing. A unidirectional electrical steel sheet with excellent magnetic properties can be obtained by holding the steel sheet at a temperature range of 50 to 300°C for 1 minute or more between the rapid cooling of the hot-rolled sheet annealing and the first cold rolling. The present invention provides a method for manufacturing. Furthermore, in addition to the above method, at least once between multiple passes in the first cold rolling, the steel plate is
The object of the present invention is to provide a method for manufacturing a unidirectional electrical steel sheet with even better magnetic properties by holding the magnetic material for a time of at least 1 minute. That is, the present inventors applied AlN as the main inhibitor to a hot-rolled silicon steel sheet through two or more cold rolling steps, including hot-rolled sheet annealing and final cold rolling with a reduction rate of more than 80% to 95%. In a manufacturing method that sequentially performs intermediate annealing, decarburization annealing after final cold rolling, and final finish annealing, we have developed a method to solve the problem that it becomes difficult to obtain high magnetic flux density as the product plate thickness becomes thinner. As a result of our investigation, we found that by holding the steel plate at a temperature range of 50 to 300°C for more than 1 minute between the rapid cooling of hot-rolled plate annealing and the first cold rolling, we could reduce the thickness to, for example, 0.170 mm. It has been found that high magnetic flux density can be obtained even with a thin material, and therefore the iron loss characteristics are further improved. Furthermore, in addition to the above findings, it is possible to further improve the magnetic properties by holding the steel plate in a temperature range of 50 to 400°C for at least one minute at least once between multiple passes in the first cold rolling. It was found that the characteristics were improved. These two findings are completely new and cannot be found in conventional methods. The present invention will be explained in detail below. The components of the hot-rolled sheet, which is the starting material of the present invention, are: Si: 2.5-4.0%, C: 0.03-0.10%, acid-soluble
Al: 0.010~0.065%, N: 0.0010~0.0150%,
It is necessary to contain Mn: 0.02 to 0.30% and S: 0.005 to 0.040%. If Si exceeds 4.0%, embrittlement becomes severe and cold rolling becomes difficult, which is not preferable. On the other hand, if it is less than 2.5%, the electrical resistance is low and it is difficult to obtain good iron loss characteristics. If C is less than 0.03%, the amount of γ before decarburization annealing becomes extremely small, resulting in an inappropriate metal structure after decarburization annealing. On the other hand, if it exceeds 0.10%, decarburization will be poor, which is not preferable. Acid-soluble Al and N are basic components for obtaining the main inhibitor AlN, which is essential for obtaining a high magnetic flux density in the present invention. If outside the above range, secondary recrystallization becomes unstable, so the acid-soluble Al is 0.010. ~
0.065%, and N is 0.0010 to 0.0150%. Mn and S are elements necessary to form the inhibitor MnS. If outside the above range, secondary recrystallization becomes unstable, so Mn is 0.02 to 0.30% and S is
Set at 0.005-0.040%. Of course, other known inhibitor constituent elements such as Sn, Sb, Cu, Cr, Se, As, and Bi may also be contained. The present invention uses a hot-rolled silicon steel sheet containing the above components as a starting material, and anneales the hot-rolled sheet to a rolling reduction of more than 80%.
The premise is a process in which cold rolling is performed two or more times including final cold rolling with a strong reduction of 95%, intermediate annealing performed in between, decarburization annealing after the final cold rolling, and final finish annealing in sequence. The manufacturing method of the present invention will be explained below. First, a hot-rolled sheet having the above components is subjected to hot-rolled sheet annealing.
During this annealing, the hot rolled sheet is held at 700 to 1200°C for 30 seconds to 30 minutes, and then cooled to 300°C at a rate of 1°C/sec or more. Next, the rapid cooling of hot rolled sheet annealing, which is a feature of the present invention, and 1
The heat treatment conditions during the second cold rolling and the reasons for their limitations will be described. Between the rapid cooling of hot-rolled sheet annealing and the first cold rolling,
It is necessary to hold the steel plate in a temperature range of 50 to 300°C for a period of one minute or more. As a result of conducting various experiments with the aim of improving the magnetic properties of products by controlling the deformation structure during the first cold rolling, we found that controlling the state of C and N is extremely important. was inferred. Therefore, based on this knowledge, heat treatment was performed under various conditions between the rapid cooling of hot-rolled sheet annealing and the first cold rolling, and the influence on the magnetic properties of the product was investigated. The results are shown below. FIG. 1 shows the relationship between the magnetic properties and the heat treatment temperature performed between the rapid cooling of hot-rolled sheet annealing and the first cold rolling. In this case, Si: 3.27% as the starting material,
C: 0.079%, acid-soluble Al: 0.025%, N: 0.0078
%, Mn: 0.073%, S: 0.024% 2.3mm
A thick hot-rolled plate was used, and the hot-rolled plate was held at 1000°C for 3 minutes and then rapidly cooled. Thereafter, it was pickled and heat treated by holding it at each temperature for 2 hours. After that, it is made into a thickness of 1.25 mm with a reduction rate of about 46%, followed by intermediate annealing by a known method, final cold rolling to finish to 0.170 mm, decarburization annealing, application of a baking separation agent mainly composed of MgO,
Final annealing and tension coating were performed. As is clear from FIG. 1, the heat treatment temperature range for improving magnetic properties is 50 to 300°C. FIG. 2 shows the relationship between the retention time of the heat treatment performed between the rapid cooling of the hot-rolled sheet annealing and the first cold rolling, and the magnetic properties. However, the heat treatment temperature is 100℃,
The process conditions other than the starting material, the heat treatment during the quenching of the hot-rolled plate annealing and the first cold rolling were the same as in the experiment described in FIG. 1. As is clear from FIG. 2, heat treatment for 1 minute or longer has the effect of improving magnetic properties. From FIG. 1 and FIG. 2, the heat treatment conditions between the rapid cooling of hot-rolled sheet annealing and the first cold rolling were defined. That is, between the rapid cooling of the hot-rolled sheet annealing and the first cold rolling, the steel sheet is held in a temperature range of 50 to 300° C. for a period of one minute or more. Although there is no particular upper limit to the heat treatment time, considering productivity, it is desirable to select a temperature so that aging ends in 50 hours or less. When the heat treatment temperature is low, it is preferable to make the heat treatment time longer;
When the temperature is 100°C, it is preferable to perform the heat treatment for 5 minutes or more. There are no particular restrictions on the heat treatment method, such as hot-rolled plate annealing to rapidly cool the sheet to 50 to 300°C, then forming it into a coil and slowly cooling it, or heat treatment in an annealing furnace, oil or hot water tank prior to the first cold rolling. A method of heating a coil in a coil unwinding stand of a cold rolling mill, etc. may be utilized. After the heat treatment, the first cold rolling is performed. If the steel sheet is held in a temperature range of 50 to 400° C. for a period of 1 minute or more at least once between the multiple passes of this first cold rolling, the magnetic properties are further improved. FIG. 3 shows the relationship between interpass aging temperature and magnetic properties in the first cold rolling. In this case, the starting materials are Si: 3.22%, C: 0.076%, acid-soluble Al:
0.025%, N: 0.0086%, Mn: 0.075%, S:
A 2.3 mm thick hot rolled sheet containing 0.025% was used, and the hot rolled sheet was held at 1000° C. for 3 minutes and then rapidly cooled.
After that, it was pickled and kept at 100℃ for 2 hours.
Aging treatment was carried out by holding each temperature for 5 minutes twice between passes of the first cold rolling to obtain a thickness of 1.25 mm at a reduction rate of about 46%. After that, intermediate annealing is performed using a known method.
A final cold rolling under heavy pressure to finish to 0.170mm, decarburization annealing, application of a seizing separation agent mainly composed of MgO, final finishing annealing, and tension coating were performed. Third
As is clear from the figure, the aging temperature range for improving magnetic properties is 50 to 400°C. FIG. 4 shows the relationship between the holding time of the interpass aging in the first cold rolling and the magnetic properties. However, the thickness of the steel plate was changed from 2.3 mm to 1.25 mm by the first cold rolling, and the steel plate was held at 100° C. for various times at a stage where the thickness reached 1.6 mm. The starting material and process conditions other than the first cold rolling were the same as in the experiment described in FIG.
As is clear from FIG. 4, aging treatment for 1 minute or longer has the effect of improving magnetic properties. The interpass aging conditions of the first cold rolling were defined from FIGS. 3 and 4. That is, the steel plate is held in a temperature range of 50 to 400° C. for a period of 1 minute or more at least once between multiple passes in the first cold rolling. Although there is no particular upper limit to the aging time, in consideration of productivity it is desirable to select a temperature so that the aging ends in 5 hours or less. If the aging temperature is low, it is necessary to lengthen the aging time. A single aging treatment is effective, but magnetic properties are further improved by alternately repeating rolling and aging treatments. The aging temperature can also be obtained by using processing heat during cold rolling, but if the temperature is insufficient, heating equipment or annealing equipment may be used. The reduction rate of the first cold rolling is not limited, but it is 10
A range of ~80% is appropriate in terms of magnetic stability. Although the mechanism of the effect of the heat treatment between the rapid cooling of hot-rolled sheet annealing and the first cold rolling, which is a feature of the present invention, is not necessarily clear, the inventors of the present invention think as follows. Figure 5 shows the above heat treatment conditions and the Bitukas hardness after the first cold rolling (loading: 1 kg).
(measured in the cross section in the width direction at the center of the plate thickness) is shown. In this case, the starting material is a 2.3 mm thick hot rolled sheet having the same composition as that described in FIG. Such a hot-rolled plate
It was held at 1000°C for 3 minutes and then rapidly cooled. After that, the steel plate was pickled, no treatment was carried out, and the steel plate was kept at 100℃ for 2 hours.
The steel plate was heat treated at 400°C for 1 hour.
Thereafter, it was cold rolled to a thickness of 1.25 mm. As can be seen from FIG. 5, in the case of the history, which is the condition of the present invention,
Hardness increases after cold rolling. By performing the heat treatment of the present invention, solid solution C and N stick to dislocations, or fine carbides and fine nitrides are formed, which impede the movement of dislocations during cold rolling, thereby affecting the deformation mechanism. It is thought that this may have had an impact.
As a result, as shown in FIG. 5, it is thought that the hardness after the first cold rolling increases. Intermediate annealing, where the effects of this change in deformation mechanism continue, 80
It is thought that the cold rolling with a final strong reduction of more than % and eventually the secondary recrystallization phenomenon during final annealing improves the magnetic properties of the product. Although the mechanism of the effect of interpass aging in the first cold rolling, which is another feature of the present invention, is not necessarily clear, the inventors of the present invention think as follows. Figure 6 shows a relationship diagram between the interpass aging conditions in the first cold rolling and the Bitukas hardness after cold rolling (measured under a load of 1 kg, at the center of the plate thickness, in a section in the width direction). In this case, the starting material is a 2.3 mm thick hot rolled sheet having the same composition as that described in FIG. The hot rolled sheet was held at 1000°C for 3 minutes and then rapidly cooled. After that, it was pickled, kept at 100℃ for 2 hours, and then 1.25mm.
Cold rolled to 1.84 in such cold rolling
mm, no treatment at each intermediate board thickness stage of 1.47 mm,
Aging treatment was carried out by holding the steel plate at 100°C for 5 minutes and the steel plate at 500°C for 5 minutes. As can be seen from FIG. 6, the hardness after cold rolling is high under the conditions of the present invention. By performing the aging treatment of the present invention, solid solution C and N are fixed to dislocations formed by cold rolling, or fine carbides are formed.
It is thought that the formation of fine nitrides interferes with dislocation motion, thereby affecting the deformation mechanism. As a result, as shown in FIG. 6, it is thought that the hardness after the first cold rolling increased. It is thought that the effect of this change in the deformation mechanism is ultimately carried over to the secondary recrystallization phenomenon during final annealing, improving the magnetic properties of the product. Intermediate annealing is performed by a known method. The magnetic properties are further improved by increasing the heating rate and performing rapid cooling. The reduction ratio of the final strong reduction cold rolling must be more than 80% to 95%. If it is less than 80%, it is difficult to obtain a high magnetic flux density, and if it exceeds 95%, secondary recrystallization becomes unstable, which is not preferable. When aging treatment is performed between passes of this cold rolling, the magnetic properties are further improved. After final cold rolling under heavy reduction, decarburization annealing is carried out by a known method.
The product is made by applying an annealing separator mainly containing MgO and performing final annealing. If the steel plate is coated with tension after final annealing, the magnetic properties will be further improved. Examples will be described below. [Example] Example 1 Si: 3.22%, C: 0.076%, acid-soluble Al: 0.026
%, N: 0.0086%, Mn: 0.073%, S: 0.025%,
A 2.3 mm thick hot rolled sheet containing Sn: 0.12% and Cu: 0.07% was annealed at 1000°C for 3 minutes (soaking) and then rapidly cooled, followed by pickling and no subsequent treatment.
100℃ x 1 hour (soaking), 400℃ x 1 hour (soaking)
Three types of heat treatment were performed. Thereafter, it was cold rolled to a thickness of 1.25 mm. Subsequently, intermediate annealing is performed using a known method.
0.170 by performing final strong reduction rolling with a reduction ratio of approximately 86%.
mm. The obtained cold-rolled sheet was subjected to decarburization annealing, application of an annealing separator, final annealing, and tension coating by known methods to obtain a unidirectional electrical steel sheet. Table 1 shows the relationship between the history of the material and the magnetic properties of the product.

[Table] Example 2 Si: 3.15%, C: 0.073%, acid-soluble Al: 0.025
%, N: 0.0082%, Mn: 0.075%, S: 0.025%. 2.3 mm thick hot rolled plate 1100℃ x 3 minutes (soaking)
The hot-rolled sheet was annealed and then rapidly cooled, followed by pickling, followed by two types of heat treatment: no treatment and 100°C for 30 minutes (soaking). Thereafter, the first cold rolling was performed to obtain a thickness of 1.35 mm. Subsequently, intermediate annealing and final heavy reduction rolling with a reduction ratio of about 86% were performed using a known method to obtain a thickness of 0.195 mm. The obtained cold-rolled sheet is subjected to decarburization annealing, application of an annealing separator, final finish annealing, and
A unidirectional electrical steel sheet was obtained by applying tension coating. Table 2 shows the relationship between the history of the material and the magnetic properties of the product.

[Table] Example 3 Si: 3.27%, C: 0.079%, acid-soluble Al: 0.025
%, N: 0.0078%, Mn: 0.073%, S: 0.024%,
A 2.3 mm thick hot rolled sheet containing Sn: 0.13% and Cu: 0.06% was annealed at 1000°C for 3 minutes (soaking) and then rapidly cooled, followed by pickling, followed by 100°C x 10 A heat treatment was performed for 30 minutes (soaking). After that, it was pickled and cold rolled for the first time to a thickness of 1.25 mm. The intermediate thickness stage of the first cold rolling is 1.84 and 1.47 mm.
No treatment when thick, 100℃ x 5 minutes (soaking),
200℃ x 5 minutes (soaking), 500℃ x 5 minutes (soaking),
Five treatments were performed at 50°C for 30 seconds (soaking).
Subsequently, intermediate annealing and final heavy reduction rolling with a reduction ratio of approximately 86% were performed using a known method to obtain a thickness of 0.170 mm. The obtained cold-rolled sheet was subjected to decarburization annealing, application of an annealing separator, final finish annealing, and tension coating by known methods to obtain a unidirectional electrical steel sheet. Table 3 shows the relationship between the history of the material and the magnetic properties of the product.

〔Effect of the invention〕

As described above, according to the present invention, a unidirectional electrical steel sheet with good magnetic properties can be stably obtained by performing heat treatment between the rapid cooling of hot-rolled sheet annealing and the first cold rolling. Therefore, its industrial effects are large. In addition to the above heat treatment, interpass aging in the first cold rolling further improves the magnetic properties, so the industrial effect is even greater.

[Brief explanation of drawings]

Figure 1 is a diagram of the relationship between the heat treatment temperature and magnetic properties performed between the rapid cooling of hot-rolled sheet annealing and the first cold rolling, and Figure 2 is a diagram of the relationship between the retention time of the heat treatment and magnetic properties. , Figure 3 is a diagram showing the relationship between the interpass aging temperature and magnetic properties in the first cold rolling, Figure 4 is a diagram showing the relationship between the retention time of the above aging treatment and magnetic properties, and Figure 5 is the relationship between the above heat treatment conditions. FIG. 6 is a diagram showing the relationship between the aging treatment conditions and the Bitchus hardness after the first cold rolling.

Claims (1)

[Claims] 1% by weight: Si: 2.5 to 4.0%, C: 0.03 to 0.10%,
Acid soluble Al: 0.010~0.065%, N: 0.0010~
0.0150%, Mn: 0.02~0.30%, S: 0.005~0.040
A hot-rolled silicon steel plate containing % is subjected to hot-rolled plate annealing,
Unidirectional properties are obtained by cold rolling two or more times, including final cold rolling with a reduction ratio of more than 80% to 95%, intermediate annealing in between, decarburization annealing after the final cold rolling, and final finish annealing. In the method for manufacturing an electrical steel sheet, the steel sheet is held in a temperature range of 50 to 300°C for a period of 1 minute or more between the rapid cooling of the hot-rolled sheet annealing and the first cold rolling. A method for manufacturing excellent unidirectional electrical steel sheets. 2 Si: 2.5 to 4.0%, C: 0.03 to 0.10%, by weight%
Acid soluble Al: 0.010~0.065%, N: 0.0010~
0.0150%, Mn: 0.02~0.30%, S: 0.005~0.040
A hot-rolled silicon steel plate containing % is subjected to hot-rolled plate annealing,
Unidirectional properties are obtained by cold rolling two or more times, including final cold rolling with a reduction ratio of more than 80% to 95%, intermediate annealing in between, decarburization annealing after the final cold rolling, and final finish annealing. In the method for manufacturing an electrical steel sheet, between the rapid cooling of the hot rolled sheet annealing and the first cold rolling,
The steel plate is held in a temperature range of 50 to 300°C for at least 1 minute, and the steel plate is heated at 50 to 400°C at least once between multiple passes in the first cold rolling.
1. A method for producing a unidirectional electrical steel sheet with excellent magnetic properties, characterized by holding the sheet in a temperature range of 1 minute or more.